Effect of nip force on ink transfer in high resolution roll-to-roll printing

Abstract

In this paper, the effect of the nip force on the ink transfer in gravure printings was investigated. An adhesive force-based ink transfer model was suggested. This model is a function of the contact length between the ink and the substrate. The static simulation of the elastic deformation of the substrate was implemented under different nip forces. The simulation showed that the contact length (L IS ) was increased as the nip force increased. Accordingly, the ink transfer ratio was increased as the nip force increased due to an increased contact length L IS . However, the fidelity of the printed pattern at high resolutions could deteriorate if the nip pressure was too high, especially when the doctoring ratio was greater than 1. Finally, experiments were conducted to verify the effect of the nip force, which showed good agreements with predicted results. The results of this study may be used as practical guidelines in determining the optimal range of the nip force in R2R gravure printing at high resolutions. NOMENCLATURE η T = Ink transfer ratio η I = Inking ratio η D = Doctoring ratio η P = Printing ratio V f = Filled volume V cell = Cell volume V r = Remained volume V p = Printed volume F IC = adhesive force at ink-cell interface F IS = adhesive force at ink-substrate interface F I = cohesive force of ink W IC = work of adhesive at ink-cell interface W IS = work of adhesive at ink-substrate interface L IC = contact length at ink-cell interface L IS = contact length at ink-substrate interface p n (z) = Distribution of the pressure b = Footprint R eq = Equivalent radius R nip = Nip roller radius R print = Printing roller radius w nip = Printing roller width δ = Indentation t rub = Rubber layer thickness ν rub = Rubber Poisson ratio E 0 ) = Young's modulus of rubber F N = Nip force V before = Volume of the printed pattern before drying V after = Volume of the printed pattern after drying M Ag = Silver mass M H2O = Water mass ρ Ag = Water density ρ H2O = Water density wt = Solid content w cell = Cell width d cell = Cell depth L cell = Cell Length w * p = Printed pattern width after drying t * p = Printed pattern depth after drying L * p = Printed pattern Length after drying

Roll‐to‐Roll Fabrication of Solution Processed Electronics

“…Obviously, this situation requires a compromise in line dimensions and overall conductance, which can be shifted toward smaller structures only by increasing the specific conductivity. Three studies dedicated to the line width optimization and the ink transfer for the R2R gravure printing of silver nanoparticle inks on PET film have been published by Nguyen et al At line speeds of 2–10 m min −1 , the authors obtained lines as narrow as 21 μm and demonstrated that air nip pressure and ink viscosity were the factors determining the line width, whereas for the height of the printed structures, the inks viscosity alone was dominant. Too high conductive structures, however, are not preferred in many cases, because coverage over a steep step can disturb the uniform and continuous deposition of subsequent functional layers, be it from solution or by dry techniques.…”

Resistance Control of an Additively Manufactured Conductive Layer in Roll-to-Roll Gravure Printing Systems

“…If F IS and F I are larger than F IC , the ink filled in the engraved cell is completely transferred to the web [22]. F IS is proportional to the product of the work of adhesive forces at the interface between the ink and web (W IS ) and the contact length between the web and ink (L IS ) [15]. If the nip pressure increases, L IS is increased, as shown in Fig.…”

“…Gravure printing is a good candidate for making conductive patterns in the R2R process because of the long life of its printing roll and its high compatibility with the R2R process [13]. However, the behavior of ink in the printing phase is more complex than that of inkjet printing, spray, and slot-die coating, and several printing factors such as web speed and nip pressure have a major interactive effect on the printing quality, which significantly affects the performance of electronic devices such as thin film transistors and flexible capacitors [14][15][16]. Several research groups have attempted to improve printing quality and resolution.…”

Versatile printed microheaters to enable low-power thermal control in paper diagnostics

“…44 Meanwhile, a more traditional rollto-roll system reached a linewidth of 20 μm by adjusting the force applied between the rollers involved in ink application. 45 We characterized the IR heating profiles for each power input in relation to overall microheater performance of the two microheater designs used in subsequent application-based experiments (Fig. S4 †).…”